1. Field of the Invention
The subject invention relates to hard drives and, more particularly for controlling the heat generated by the hard disk drive heads preamp.
2. Related Art
FIG. 1a depicts a prior art hard drive 100 with the cover removed, while FIG. 1b depicts an enlarged image of the preamp area. The hard disk 100 uses rotating platters (disks) 110 to store data. Each platter is rotated by a spindle (not shown) and has a smooth magnetic surface on which digital data is stored. Information is written to the disk by applying a magnetic field from a read-write head (not shown) that is attached to an actuator arm 120. For reading, the read-write head detects the magnetic flux emanating from the magnetic bits that were written onto the platter. Since the signals from the read/write head is very faint, a preamp 130 is provided in close proximity to the head. The preamp 130 is a chip that is mounted on a substrate 140. The substrate 140 is mounted onto a carrier plate 150, that connects to the actuator arm assembly 120. The flexible circuit loop 160 is connected to the substrate 140, to transfer signals between the preamp 130 and the associated electronics (not shown). The associated electronics control the movement of the actuator and the rotation of the disk, and perform reads and writes on demand from the disk controller.
FIG. 2 depicts a prior art preamp sub-assembly, showing a carrier plate 250, upon which the substrate 240 is mounted. The preamp 230 is attached to the substrate 240 and makes electrical connections to tap points on the substrate 240. As shown in the cross-section inside the broken-line callout, the substrate is generally made of a stainless steel or aluminum backing, generally referred to as a stiffener, 215, an insulating polyimide layer 225, and copper conducting contacts and lines 235. The “legs” of the preamp chip 230 (or bumps in case of a flip chip) are soldered to the copper contacts 235. In the case depicted, substrate 240, having its own stiffener 215, folds back a top carrier plate 250. Carrier plate 250 and stiffener 215 can be made from a common metal layer. Alternate designs integrate the function of the carrier plate into the stiffener, eliminating the need for the carrier plate. The substrate is generally made using a sheet of stiffener material, upon which several substrates are formed, as illustrated in FIG. 3. As depicted in FIG. 3, a sheet of stiffener material, such as stainless steel or aluminum, 315, serves as a starting material for fabricating the substrate 345. For each substrate 345, a polyimide layer 325 is deposited on top of the stiffener 315 to serve as an electrical insulator. On top of the polyimide various conductive elements 335 are deposited to form contacts and transmission lines. The fabrication of these layers is done using conventional photolithography techniques. Both subtractive and additive flexible circuit fabrication processes are commonly employed in hard disk drives. To maximize the available real estate, the substrates 345 are fabricated so as to “nest” with each other, and after the fabrication is completed the substrates 345 are cut out of the stiffener sheet 315.
As the physical size of the hard drive decrease, the heat generated by the preamp affects performance and reliability of the hard drive.